Re: Magnesium decks?

Actually that was one of the main problems with that kind of deck, and unless you want to put ugly screwed on patches you can't really fix them. Not worth anything scrapping either, nobody will pay scrap for them because you can't recycle magnesium like most metals. To me the lawn boy deck design was the best designed mower deck out there but using magnesium wasn't the smartest thing!! But that's just my opinion!!

Re: Magnesium decks?

Originally Posted by parkboy

Is oxidation - pin holes in older magnesium LB decks common? Is it a problem?

From my experience the pitting issue is common, but worse than that is the cracking. It seems like the mag decks were quite brittle. I think if you can find an older mag deck Lawn Boy with minimal pitting and no cracks or chunks missing, you've made a good find.

Re: Magnesium decks?

Yes the pitting and cracking is more common on a mag deck than an aluminum deck. Magnesium can be welded using an Heliarc welder in A.C. mode with pure magnesium rods. I have had a couple of cracks welded on a 1966 restore back in 2012 and it turned out well. Those mag decks just seem to develop cracks out of no where, in areas that you wouldn't even think were stress points. The big problem these days is the price of pure magnesium welding rods. The welder that did my work says it cost him 90 bucks a pound, so if I want anymore mag welding done I will have to supply the rods myself.

As far as the pitting goes, I think what works really great is a product called Lab Metal (high temp version). If you clean the metal good, media blasting preferred, then you can apply the Lab Metal over the pits, sand it relatively smooth, then take it to the powder coat shop to get it baked and powder coated and it will be almost as good as new. I think some enterprising young person who has the right equipment, knowledge and lives where there are plenty of old mag decks laying around could make good money refurbishing those decks in this manner and selling on ebay. I think someone has already been doing that with the newer aluminum decks.

Re: Magnesium decks?

Remember the famous film about the Lockheed Comet.
The tail used to simply fall off.
It was found to be caused by stress corrosion cracking & metal fatigue.
All metals do this & you use it when you break a piece of wire by bending it backwards & forewards .
Back when the decks were made little was known about magnesium so they just substituted magnesium for aluminium in a mould for aluminium which did not work because the metals are not the same.

Scrap yards do not like having magnesium around because of the fire risk so unless they supply to a foundry that casts magnesium they do not touch it.
magnesium is poision to most aluminium foundries and if they find magnesium in a load of aluminium they will reject the load.
If you run magnesium through a metal shredder it usually explodes.
So yes it can be a problem to recycle.

OTOH it is worth around twice what aluminium is as scrap to some one who wants it.

Re: Magnesium decks?

I have a Lawn Boy 19" with a magnesium deck and I just love it for mowing our front bank, it's much more lightweight than our other push mowers. The deck on mine has been welded by a previous owner and looks like they did a great job! It's probably a TiG welding process, doubt you could weld it with any other welder. Problem with mine right now is it's not running and I can't figure out what the problem is. I'll have to put in a bit more time and try some different parts and maybe it will run again..

Re: Magnesium decks?

You say your little 19 mag deck mower is not running, can you elaborate on that? Maybe we can help if we have a bit more info on the symptoms. Model number would be good. Will it fire at all, or does it run for a short time, then falter?

Re: Magnesium decks?

Originally Posted by Lawnboy77

You say your little 19 mag deck mower is not running, can you elaborate on that? Maybe we can help if we have a bit more info on the symptoms. Model number would be good. Will it fire at all, or does it run for a short time, then falter?

Yes, it will fire after you prime it then it runs for a short while and dies. It starts right back up with a prime, in fact you can keep it running if you prime it while it's running. I've tried different carburetors, at least one of the carbs came off a running mower but wouldn't make mine run. I feel like it might be in the fuel tank because when you take the line off the fuel just dribbles out and that's with the cap off. I cleaned out the line and blew through the outlet with compressed air and it appears to be clear. My next move might be to look at the on/off fuel valve but I'm not holding my breath. I put new crank seals in it earlier in the week so it's not that I guess. I'll try to get the model number tomorrow but it's an F series engine with the plastic carb.

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